1. Field of the Invention
The invention relates to image processing apparatus and method for performing an image process in which a quantity of recording material is limited.
2. Related Background Art
In an ink jet recording system, an ink containable quantity in a recording medium is determined by characteristics of the recording medium. Particularly, in case of a color recording, when the recording exceeding a limit of the ink containable quantity of the recording medium is executed, a blur occurs at the boundary of each color.
Now, assuming that an ink droplet forming one pixel has a quantity of 40 pl (picoliter) per color, an emission or implantation quantity of the ink droplet per area is equal to about 220% in case of a normal paper, about 280% in case of a coated paper, about 300% in case of an OHP sheet for ink jet, and 340% in case of a glossy film for ink jet. As mentioned above, the emission or implantation quantity of ink differs every recording medium.
A recording technique for increasing or decreasing an ink emission or implantation quantity per area by modulating a size of emission droplet in accordance with the kind of recording medium has been proposed.
There has also been proposed a recording technique such that a ratio at which a pixel to form a black dot is generated is set to a value that is equal to or larger than a generation ratio at which yellow, magenta, and cyan dots are generated in the same pixel and a process to emit or implant none of the yellow, magenta, and cyan dots is performed to the pixel into which the black dot is emitted or implanted.
There has also been proposed a recording technique such that the minimum value (undercolor) in the multivalue levels of yellow, magenta, and cyan in one pixel is converted into a multivalue level of black and a conversion amount is subtracted from the multivalue levels of yellow, magenta, and cyan in one pixel.
However, in case of the ink jet recording system, it is difficult to modulate the ink emission quantity by an amount of about 30% in one ink droplet emitting mechanism, so that the recording apparatus cannot help having a complicated construction.
In case of the method of generating a black pixel in correspondence to the generation ratio at which yellow, magenta, and cyan dots are generated in the same pixel or the method of converting a part of the undercolor into black, it is impossible to restrict an emission or implantation quantity of the secondary color which is expressed by only yellow and magenta, cyan and yellow, or magenta and cyan.